Hydraulic forming press



July 26, 1966 Q M|THELL 3,262,294

HYDRAULIC FORMING PRESS Filed Aug. 16, 1963 .3 Sheets-Sheet 1 F57 I .4 L I 1j '1' 11 INVENTOR, CHARLES L. MITCHELL BY; g' 1 ;E%7.MM

ATTORNEYS y 1956 c. L. MITCHELL 3,262,294

HYDRAULI 0 FORM I NG PRES S Filed Aug. 16, 1963 6 Sheets-Sheet 2 Fig.2 12

July 26, 1966 Filed Aug. 16, 1963 C. L. MITCHELL HYDRAULIC FORMING PRESS 3 Sheets-Sheet 3 I E I Fig.4

United States Patent 3,262,294 HYDRAULIC FORMING PRESS Charles L. Mitchell, Cincinnati, Ohio, assignor to The Cincinnati Milling Machine Co., Cincinnati, Ohio, a corporation of Ohio Filed Aug. 16, 1963, Ser. No. 302,567 8 Claims. (Cl. 72-63) The present invention relates to a hydraulic forming press.

In one type of hydraulic forming press, two members thereof are mounted in telescopic relation. A flexible diaphragm secured across one end of the outermember defines, with the inner and outer member, a chamber which is expanded and contracted when relative movement between the inner and outer members occur. A reservoir for hydraulic fluid supplies fluid to the chamber as it expands, and receives fluid from the chamber as it contracts, preferably through a passage in the inner member which terminates at an opening in the chamber. A bed to receive workpiece blanks is provided, preferably below the chamber, and .a male die is slidably received in the bed for vertical movement. In a forming operation of a press of this type, the outer telescoping press member descends to the bed for engagement of the flexible die member with the workpiece blank, the chamber expanding and receiving fluid from the reservoir during this closing movement. After the chamber has been expanded, pressure in the chamber is raised, as, for ex- .ample, by supplying additional fluid under high pressure to the expanded chamber. Thereafter, the male die is raised, urging the workpiece blank into the flexible die member, and the pressure in the chamber, acting through the flexible member, shapes the workpiece blank in accordance with the shape of the male die. As the male die is raised, the flexible die member is deflected upwardly, contracting the chamber. Usually fluid must be released from the chamber as the male die is raised to maintain the desired pressure level in the chamber. After the male die has been raised to form the workpiece, pressure is released from the chamber, and the outer press member is raised for removal of the finished workpiece, contracting the chamber and returning the fluid therein to the reservoir as the press is opened.

One difiicu-lty encountered heretofore in presses of this type occurred when the chamber was rapidly expanded to bring the flexible diaphragm down onto the workpiece blank. Because of a partial vacuum created in the chamber by the rapid expansion thereof, the flexible die member had a tendency to bow inwardly, leaving an air pocket between the flexible die member and the workpiece blank when the flexible die member engaged the workpiece blank. The air pocket had a deleterious effect on formation of the workpiece and, .to avoid the air pocket, the rate of descent of the flexible die had to be reduced with a consequent increase in the cycle time for each workpiece.

In the present invention, a partition is provided in the chamber, dividing the chamber into sections, one section in communication with the opening through which fluid passes to and from the chamber, and another section in communication with the flexible die member. In the preferred form of the invention, the partition, which is secured in the same telescoping member as the flexible diaphragm, has at least two passages extending therethrough, each having a check valve therein. The two check valves are normally closed and remain closed when the flexible diaphragm is rapidly lowered to the bed to engage the workpiece blank. Thus, it is only the upper section of the chamber which expands. Since there is no expansion of the lower section of the chamber, no

3,262,294 Patented July 26, 1966 partial vacuum is created therein. The flexible diaphragm, in communication only with the lower section of the chamber, engages the workpiece blank over its entire span, without air pockets being formed between the workpiece blank and the flexible diaphragm. When the pressure in the upper section of the chamber is raised, one check valve opens to allow this high pressure to be communicated to the lower section of the chamber. When the male die urges the workpiece blank into the flexible diaphragm to contract the lower chamber section, the other check valve (which is directed oppositely to the first check valve) opens to release fluid from the lower sect-ion.

In addition to eliminating undesirable air pockets between the diaphragm and the workpiece blank, the partition, since it divides the pressure chamber into sections, limits the amount of fluid lost if the flexible diaphragm should rupture during forming.

It is therefore one object of the present invention to prevent the formation of air pockets between a workpiece blank and the flexible diaphragm of a hydraulic forming press.

It is another object of the present invention to limit the loss of oil when rupture of the flexible diaphragm of a hydraulic press occurs during forming.

Other objects and advantages of the present invention should be readily apparent by reference to the following specification, considered in conjunction with the accompanying drawings forming a part thereof, and it is to be understood that any modifications may be made in the exact structural details there shown and described, within the scope of the appended claims, without departing from or exceeding the spirit of the invention.

In the drawings:

FIG. 1 is a cross-sectional view of a hydraulic forming press incorporating the present invention;

FIG. 2 is a view taken on the line 2-2 of FIG. 1;

FIG. 3 is an enlarged view, taken as the view of FIG. 1, of the lower section of the pressure chamber before formation of the workpiece begins; and

FIG. 4 is a view similar to the view of FIG. 3 except that it shows the lower section of the pressure chamber during formation of the workpiece.

There is shown in FIGS. 1 and 2 a hydraulic forming press having a bed 10, a head section 11 above the bed,

and four vertical support members '12 extending from the bed to support thehead member. The head member 11 has a cylindrical depending portion 11a, and a sleeve 13 is slidably received over the depending portion 11a for vertical movement thereon. Two cylindrical chambers 14 in the head member 11 each slidably receive therein a piston 15 which is connected by rod 15a to the sleeve 13. Chambers 14 and pistons 15 define motors which, under the control of four-way valve .16, operate to raise and lower the sleeve 13.

A diaphragm .17, constructed of rubber or other flexible material, is received in the lower end of the sleeve 13 and secured therein by ring clamp 18 to define a chamber 19 bounded by the lower end of head member portion 11a, the sleeve 13, and the diaphragm 17. The head member 11 has a reservoir 20 for hydraulic fluid, and a passage 21 extends from reservoir 20 through depending portion 11a to an opening 22 into chamber 19. A valve 23 in passage 21 permits selective communication between reservoir 20 and chamber 19.

The bed member 10 which receives a workpiece blank 24 has an opening 25 in which a male die member 26 is slidably received. A cylindrical chamber 27 in the bed 10, and a piston 28 slidably received in the chamber 27, define a motor which is under the control of four-way valve 29. Piston 28 is connected to die memaaeaase her 26 by piston rod 30 to effect vertical movement of the die member.

Sleeve 13 has an internal circumferential groove in chamber 19 which receives a split steel ring 36. Two plates 37 and 38 are secured together by bolts 39 in straddling relation to the split ring 36 so that the plates are securely held in the sleeve 13. These plates, which extend across the chamber 19 and separate the flexible diaphragm 17 from the opening 22, define a partition which divides the chamber into two sections, an upper section 190 and a lower section 1%. Since the partition is secured in the movable sleeve 13 (the same member to which the diaphragm is secured), it is only the upper section 19a of the chamber (in communication with opening 22) which will expand as the sleeve descends to close the press. The lower section of the chamber, which is in communication with the flexible diaphragm 17, will not expand as the press closes.

There is shown six passages extending through the partition. Three passages 40 each have a check valve 41 therein which permits flow of fluid only from the upper section 1% of the chamber to the lower section 1% thereof. The other three passages 42 each have a check valve 43 therein which only permits flow of fluid from the lower section 1% of the chamber to the upper section 19a thereof. Thus, the check valves in passages 42 are directed oppositely to the check valves in the passages 40. Three fixed studs 44 extend from the bottom of stationary frame portion 11a to enter, respectively, the three passages 40 and hold check valves 41 open when the sleeve is in its uppermost position as shown in FIG. 1. When the check valves 41 are disengaged from studs 44, the spring 45 of each check valve 41 holds the check valve closed until the pressure in section 1% exceeds the pressure in section 1912 by some predetermined amount, at which time the valve opens and remains open until the pressure differential across the partition drops below that predetermined amount. In a similar manner spring 46 of check valve 43 holds the check valve closed until the pressure in section 1% exceeds the pressure in section 19a by some predetermined amount.

When the press is open (that is, the sleeve 13 is raised to its upper limit as shown in FIG. 1), a workpiece blank 24 is placed on the bed 10. The valve 23 is in the position shown in FIG. 1 .and, since the check valves 41 are held open by studs 44, chamber sections 1% and 191) are filled with low pressure fluid from reservoir 20. A pump 50 takes fluid from sump 51 and delivers it under pressure to line 52. When the movable valve member 53 of valve 16 is shifted to the left from the position shown in FIG. 1, fluid under pressure is delivered to line 54 to lower sleeve 13 until flexible die member 17 engages workpiece blank 24. As soon as sleeve 13 leaves its uppermost position, check valves 41 close and remain closed during the descent of sleeve 13. The descent of sleeve 13 may be rapid and, if the-chamber section 19a is expanded at a greater rate than fluid can flow from reservoir 20 through passage 21 to chamber section 1%, a partial vacuum will be created in that chamber section. Although, at this time, the pressure in chamber section 1% will be greater than the pressure in chamber section 19a, the pressure differential will not be great enough to open check valves 43. Therefore, none of the check valves will open during the descent of sleeve 13 and the flexible diaphragm 17, which is separated from the opening 22 by the partition, is not bowed or otherwise deformed by the partial vacuum created in the chamber section 19a by descent of sleeve 13. After the diaphragm is engaged with the workpiece blank 24, valve 23 is closed and pressure in the upper section 1% of the chamber is raised. A passage 55, having an opening 56 into chamber section 1%, extends through the depending portion 11a of head member 11 and head member 11 for connection to line 57. A high pressure pump 58 draws fluid from sump 51 and delivers it under high pressure to line 59. The maximum pressure in line 59 is determined by adjustable relief valve 69, which is set for a high valve, as, for example, 10,000 pounds per square inch. When the movable valve member 61 of valve 62 is shifted to the left after the press is closed, lines 57 and 59 are connected to introduce high pressure fluid to the upper section 1% of chamber 19.

The high pressure introduced to the upper section 19a of the chamber creates a pressure differential across the partition which opens the check valves 41 in passages 40 (as shown in FIG. 3) so that the high pressure fluid is introduced to the lower section 1% of chamber 19. When the pressure in the lower section 1% of the chamber approaches the pressure in line 59 and chamber section 1%, the check valves .-1 close. Thereafter, the movable valve member 63 of valve 29 is shifted to the right to connect pressure line 52 with motor line 64. This raises the male die 26 and urges the workpiece blank 24 into the flexible diaphragm 17 to form the workpiece around the male die member. As the male die member 26 pushes the workpiece blank 24 into flexible diaphragm 17, the lower section 1% of the chamber contracts. This contraction raises the pressure in the section 19b above the pressure in chamber section 1%, and, when a predetermined pressure differential is reached, check valves 43 in passages 42 open (as shown in FIG. 4) to permit fluid to flow through passage 55 for discharge through relief valve 60.

After the workpiece is formed, movable valve member 61 of valve 62 is shifted to the right and valve member 23 is opened to relieve pressure in chamber section 19a. Then valve member 53 of valve 16 is shifted to the right, connecting pressure line 52 to motor line 65 and connecting motor line 54 to exhaust line 66, to raise the sleeve 13. During upward movement of the sleeve, the check valves remain closed, forcing the fluid in the upper section 19a of chamber 19 back up through passage 21 into reservoir 20, until the sleeve 13 approaches its uppermost limit. At that time, the check valves 41 are opened by engagement with studs 44, and fluid can flow into bottom chamber section 19b to replace the fluid forced out of this chamber section by contraction during forming. Thereafter, valve member 63 of valve 29 is shifted to the left, connecting pressure line 52 to motor line 67 and connecting motor line 64 to exhaust line 68, to lower the male die plunger for removal of the finished workpiece.

What is claimed is:

1. In a hydraulic forming press, the combination comprising means defining an expandable pressure chamber, said means including a flexible diaphragm closing one end of the pressure chamber, said pressure chamber having an opening through which hydraulic fluid is received as the chamber expands, and a partition extending across the chamber between said opening and the flexible diaphragm to divide the chamber into two sections; said partition isolating the section of the chamber between the partition and the flexible diaphragm from the section of the chamber between the partition and the opening as the chamber expands.

2. In a hydraulic forming press, the combination comprising:

(a) means defining a pressure chamber expandable as the press closes, said means including a flexible diaphragm closing one end of the pressure chamber, said pressure chamber having an opening through which hydraulic fluid is received as the chamber expands,

(b) a partition extending across the chamber between said opening and the flexible diaphragm, said partition dividing the chamber into a first section and a second section, said first section in communication with said opening and having an increasing volume as the press closes, said second section in communication with said diaphragm and having an unchanging volume as the press closes, and

(c) means for the controlled flow of fluid between said chamber sections.

3. In a hydraulic forming press, the combination comprising:

(a) a stationary press member,

(b) a movable press member telescopically received over the stationary press member, said movable press member having a flexible diaphragm closing one end to define an expandable pressure chamber, said chamber having an opening for the introduction and evacuation of hydraulic fluid,

(c) a partition secured in the movable press member between the flexible diaphragm and the end of the stationary member to divide the chamber into a first section in communication with said opening and a second section in communication with said diaphragm, said sections having a fluid passage extending therebetween,

(d) and a valve in said passage to control the flow of fluid between said sections.

4. In a hydraulic forming press the combination comprising:

(a) means defining a pressure chamber expandable as the press closes, said means including a flexible diaphragm closing one end of the pressure chamber, said pressure chamber having an opening through which hydraulic fluid is received as the chamber expands,

(b) a partition extending across the chamber between said opening and the flexible diaphragm to restrict expanision of a section of the chamber at said one end of the pressure chamber as the press closes, said partition having a passage therethrough,

(c) and a valve in said passage to control the flow of fluid therethrough.

S. In a hydraulic forming press the combination comprising:

(a) means defining a pressure chamber expandable as the press closes, said means including a flexible diaphragm closing one end of the pressure chamber, said pressure chamber having an opening through which hydraulic fluid is received as the chamber expands,

(b) a partition extending across the chamber between said opening and the flexible diaphragm, said partition dividing the chamber into a first section and a second section, said first section expanding as the press closes and in communication with said opening, said second section unexpanding as the press closes and in communication with said diaphragm, said partition having two passages extending therethrough, and

(c) a check valve in each of said passages, said check valves normally closed and oppositely directed to permit fluid flow from the high to the low pressure side of the partition when predetermined pressure differentials are exceeded across the partition in one or the other direction.

6. In a hydraulic forming press, the combination comprising:

(a) a stationary press member,

(b) a movable press member telescopically received over the stationary press member, said movable press member having a flexible diaphragm closing one end to define an expandable pressure chamber, said chamber having an opening for the introduction and evacuation of hydraulic fluid,

(c) a partition secured in the movable press member between the flexible diaphragm and the end of the stationary member, said partition separating the flexible diaphragm from said opening,

((1) and a valve in said partition to control the flow of hydraulic fluid therethrough.

7. In a hydraulic forming press, the combination comprising:

(a) a stationary press member having an opening at one end,

(b) a movable press member telescopically received over said one end of the stationary press member, said movable press member having a flexible diaphragm closing one end to define with the stationary press member an expandable pressure chamber,

(c) a partition secured in the movable press member between the flexible diaphragm and the end of the stationary press member, said partition extending across the interior of the movable press member and having two passages therethrough,

(d) a check valve in each of said passages, said check valves normally closed and oppositely directed to permit fluid flow from the high to the low pressure side of the partition when predetermined pressure differentials are exceeded across the partition in one or the other direction.

8. A hydraulic forming press comprising in combination:

(a) a frame having a cylindrical depending portion,

(b) a sleeve slidably received over said depending portion,

(c) a flexible diaphragm secured in the lower end of said sleeve to define with the sleeve and the lower end of the depending frame portion a fluid pressure chamber,

(d) a partition secured inside the sleeve and extending thereacross to divide the pressure chamber into an upper and lower section, said partition having at least two passages extending therethrough,

(e) means to raise and lower the sleeve to contract and expand said upper section of the chamber,

(f) a fluid reservoir to supply fluid to and receive fluid from said upper section of the pressure chamber on each stroke of the sleeve,

(g) a male die member operable when the sleeve is down to extend into the flexible diaphragm and form a workpiece blank received between the male die member and the flexible diaphragm,

(h) means to raise the fluid pressure in the upper section of the pressure chamber, and

(i) a check valve in each of said partition passages, said check valves normally closed during raising and lowering of said sleeve, one of said check valves operable to permit flow from the upper section of the chamber to the lower section thereof when the pressure in the upper section is raised and the other of said check valves operable to permit flow from the lower section of the chamber to the upper section thereof when the male die member is extended into the flexible diaphragm. 

1. IN A HYDRAULIC FORMING PRESS, THE COMBINATION COMPRISING MEANS DEFINING AN EXPANDABLE PRESSURE CHAMBER, SAID MEANS INCLUDING A FLEXIBLE DIAPHRAGM CLOSING ONE END OF THE PRESSURE CHAMBER, SAID PRESSURE CHAMBER HAVING AN OPENING THROUGH WHICH HYDRAULIC FLUID IS RECEIVED AS THE CHAMBER EXPANDS, AND A PARTITION EXTENDING ACROSS THE CHAMBER BETWEEN SAID OPENING AND THE FLEXIBLE DIAPHRAGM TO DIVIDE THE CHAMBER INTO TWO SECTIONS; SAID PARTITION ISOLATING THE SECTION OF THE CHAMBER BETWEEN THE PARTITION AND THE FLEXIBLE DIAPHRAGM FROM THE SECTION OF THE CHAMBER BETWEEN THE PARTITION AND THE OPENING AS THE CHAMBER EXPANDS. 